Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Analysis of Flow Migration in an Ultra-Compact Combustor

[+] Author and Article Information
Brian T. Bohan

Deputy Branch Chief High and Low Speed Aerodynamic Configuration Branches,
Air Vehicles Directorate,
Air Force Research Laboratory,
Wright-Patterson AFB, OH 45433

Marc D. Polanka

Associate Professor
Department of Aeronautical and Astronautical Engineering,
Air Force Institute of Technology,
Wright-Patterson AFB, OH 45433

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received September 13, 2011; final manuscript received August 24, 2012; published online April 23, 2013. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(5), 051502 (Apr 23, 2013) (11 pages) Paper No: GTP-11-1312; doi: 10.1115/1.4007866 History: Received September 13, 2011; Revised August 24, 2012

The ultra-compact combustor (UCC) has the potential to offer improved thrust-to-weight and overall efficiency in a turbojet engine. The thrust-to-weight improvement is due to a reduction in engine weight by shortening the combustor section through the use of the revolutionary circumferential combustor design. The improved efficiency is achieved by using an increased fuel-to-air mass ratio and allowing the fuel to fully combust prior to exiting the UCC system. Furthermore, g-loaded combustion offers increased flame speeds that can lead to smaller combustion volumes. One of the issues with the UCC is that the circumferential combustion of the fuel results in hot gases present at the outside diameter of the core flow. These hot gases need to migrate radially from the circumferential cavity and blend with the core flow to present a uniform temperature distribution to the high-pressure turbine rotor. The current research focused on correlations to control the UCC cavity velocity, control the temperature profile throughout the UCC section, analyze the exhaust species exiting the combustor, and quantify pressure losses in the system. To achieve these goals, a computational fluid dynamics (CFD) analysis was used on a UCC geometry scaled to a representative fighter-scale engine. The analysis included a study of cavity to core flow interaction characteristics, a 5- and 12-species combustion model of liquid and gaseous fuel, and determination of species exiting the combustor. Computational comparisons were also made between an engine realistic condition and an ambient pressure rig environment.

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Fig. 1

UCC and traditional combustor systems comparison

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Fig. 2

UCC cavity equivalence ratio at blowout as a function of cavity g-loading [2]

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Fig. 3

Cross-sectional view of UCC section used in the current analysis (dimensions are in centimeters)

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Fig. 4

Origin and orientation of the hybrid vane design

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Fig. 5

Computational domain relative to full engine annulus

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Fig. 6

Computational domain for the 20 hybrid-vane configuration

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Fig. 7

Computational domain for the 30 hybrid-vane configuration

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Fig. 8

Relationship of cavity inlet velocity to cavity tangential velocity and hole diameter

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Fig. 9

Nonreacting results from preliminary analysis with five-species reacting flow results

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Fig. 10

Streamlines in the circumferential cavity as viewed from upstream (baseline inlet above, 3X inlet below)

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Fig. 11

Circumferentially averaged total temperatures at combustor section exit using the 12-species model and ideal air inlet diameters with piecewise-polynomial Cp values

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Fig. 12

Total temperature contours on UCC components for ideal tangential velocities

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Fig. 13

Isosurfaces colored by total temperature using the 12-species combustion model and ideal air inlet diameters with a 20 hybrid vane engine configuration

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Fig. 14

Circumferentially averaged mass fractions of species at combustor section exit with ideal air inlet diameters and a 20-vane engine configuration




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